title: Influence of slice thickness on diagnoses of pulmonary nodules using low-dose CT: potential dependence of detection and diagnostic agreement on features and location of nodule.
abstract: OBJECTIVE
  The aims of this study were to assess the influence of slice thickness on the ability of radiologists to detect or not detect nodules and to agree or disagree on the diagnosis and also to investigate the potential dependence of these relations on the sizes, average computed tomographic (CT) values, and locations of the nodules.
  
  
  METHODS
  Six radiologists performed qualitative diagnostic readings of multislice CT images with a slice thickness of 2 or 10 mm obtained from 360 subjects. The nodules were diagnosed as nodules for further examination (NFEs), inactive nodules for no further examination (INNFEs), or no abnormality. The results of the diagnoses were cross-tabulated and quantitatively analyzed using the average CT values, sizes, and locations of the nodules with reference to the 2-mm slices. Multivariate logistic regression analyses were used to estimate the significant associations of these parameters with the ability of radiologists to detect or not detect nodules and to agree or disagree on the diagnosis.
  
  
  RESULTS
  Totals of 130 NFEs and 403 INNFEs for 2-mm slice thickness and 142 NFEs and 338 INNFEs for 10-mm slice thickness were diagnosed. Nodule classifications were as follows: the same diagnosis on both slice thickness images (67.6%), different diagnoses on two slice thickness images (21%), missed on 10-mm slice thickness images (10.6%), and misinterpreted on 10-mm slice thickness images (0.7%). Regarding detection and nondetection, NFE diagnoses were influenced by size (odds ratio [OR], 132.50; 95% confidence interval [CI], 4.77-4711) and the average CT value (OR, 27.20; 95% CI, 3.21-645.3), and INNFE diagnoses were influenced by size (OR, 16.10; 95% CI, 6.18-55.19) and the average CT value (OR, 7.67; 95% CI, 2.19-30.91). Regarding diagnostic agreement and disagreement, the NFE diagnoses were influenced by size (OR, 3.60; 95% CI, 1.29-11.04), nodule distance from the lung border (OR, 2.85; 95% CI, 1.27-6.65), and nodule location in the right upper lobe (OR, 0.07; 95% CI, 0.003-0.477), while the INNFE diagnoses were influenced by the average CT value (OR, 11.84; 95% CI, 3.33-55.86), size (OR, 0.42; 95% CI, 0.25-0.70), and nodule distance from the lung border (OR, 0.41; 95% CI, 0.25-0.66).
  
  
  CONCLUSIONS
  The influence of slice thickness on the ability of radiologists to detect or not detect nodules and to agree or disagree on the diagnosis was quantitatively evaluated. Detection and nondetection of NFEs and INNFEs are influenced by size and average CT value. Agreement and disagreement on NFE and INNFE diagnoses are influenced not only by size and average CT value but also, importantly, by the locations of nodules.
authors.affiliation: Functional Systems Engineering, University of Tokushima, Japan.
authors.forename: Marodina
authors.initials: M
authors.lastname: Sinsuat
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Saita
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Kawata
authors.forename: Noboru
authors.initials: N
authors.lastname: Niki
authors.forename: Hironobu
authors.initials: H
authors.lastname: Ohmatsu
authors.forename: Takaaki
authors.initials: T
authors.lastname: Tsuchida
authors.forename: Ryutaro
authors.initials: R
authors.lastname: Kakinuma
authors.forename: Masahiko
authors.initials: M
authors.lastname: Kusumoto
authors.forename: Kenji
authors.initials: K
authors.lastname: Eguchi
authors.forename: Masahiro
authors.initials: M
authors.lastname: Kaneko
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Morikubo
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Moriyama
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D002452:Cell Count; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D055613:Multiple Pulmonary Nodules / Q000000981:diagnostic imaging*; D015588:Observer Variation; D011829:Radiation Dosage; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed